1. Field of the Invention
The present invention relates to a system and a method for executing preamble detection, symbol timing recovery, and frequency offset estimation, and more particularly to a system and a method that use less symbols to detect preamble symbol with the calculation of performing timing recovery and frequency offset calculation.
2. Description of the Related Art
In a Japanese personal handyphone system (PHS), the preamble of a burst has a known format of 0110, and the preamble is provided for the synchronization of a receiving system, wherein the synchronization includes a preamble detection, a symbol timing detection, and a frequency offset computation. However, the length of the preamble is fixed, and thus the number of symbols remained for executing the symbol timing detection and frequency offset computation is very limited, after the preamble is detected. A probability of error for executing the timing detection and the frequency offset computation with a limited number of symbols becomes larger, and thus it is not easy to obtain accurate timing detections and frequency offsets.
In U.S. Pat. No. 5,574,399 entitled “COHERENT PSK DETECTOR NOT REQUIRING CARRIER RECOVERY” (filed on Oct. 30, 1995 and issued at Nov. 12, 1996), a synchronous PSK detector that does not require a carrier recovery is disclosed, but such PSK detector has the following shortcomings: 1. Only phase data is used for performing the timing recovery; 2. The minimum frequency offset is not necessary a correct frequency offset in a low SNR environment, and thus its moving average value will be misled greatly.
In U.S. Pat. No. 6,038,267 entitled “DIGITAL MODULATOR, MAXIMUM-VALUE SELECTOR, AND DIVERSITY RECEIVER” (filed on Jan. 24, 1997 and issued on Mar. 14, 2000), a digital modulator maximum-value selector, and diversity receiver is disclosed, but such digital modulator has the following shortcomings: 1. A large number of symbols are needed for lowering the computational error; 2. Many buffers are needed for storing the large number of symbols.
In view of the description above, a system and a method for executing preamble detection, symbol timing recovery, and frequency offset estimation are needed for detecting the preamble symbols with less symbols while performing the timing recovery and frequency offset calculation, so as to overcome the foregoing shortcomings of the prior art.